A metaphor is there to make an even stronger image in the reader's head by describing a place, subject, or object as something unlikely.
He was a speeding bullet.
A sea of trouble.
Drowning in debt.
I am a rainbow.
The world is a stage.
Her eyes were glistening jewels.
Metaphors are used in poetry to create an image of comparison in your thoughts.
Why don't you try using metaphors in your writing and enter it into one of our writing competitions - we read every piece of work we receive and you could win prizes!